flutter - 如何在子窗口小部件上编辑值

Question

我尝试编辑子窗口小部件的值，我可以使用StatefulWidget父级来执行此操作，但我想使用StatelessWidget父级来执行此操作，而无需使用全局值

    class Homepage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        actions: <Widget>[
          FlatButton(child: Text('addFile'), onPressed: () {}),
          FlatButton(child: Text('deleteFile'), onPressed: () {})
        ],
      ),
      body: Child(),
    );
  }
}

class Child extends StatefulWidget {
  @override
  _ChildState createState() => _ChildState();
}

class _ChildState extends State<Child> {
  var hasFile = true;
  @override
  Widget build(BuildContext context) {
    return hasFile ? Text('has a file') : Text("no File");
  }
}

Answer 1

您在想错方法。子aka Text()应该从由应用程序管理或至少由上面的小部件管理的模型中获取其值。我将使用提供程序包https://pub.dev/packages/provider并执行以下操作:

import 'package:provider/provider.dart';
import 'package:flutter/material.dart';


class MyState with ChangeNotifier {
  String _myText;

  MyState(this._myText);

  getMyText() => _myText;

  void changeText(String newText) {
    _myText = newText;
    notifyListeners();
  }
}

class Homepage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
        providers: [
          ChangeNotifierProvider(builder: (_) => MyState("initial Text")),
        ],
        child: Scaffold(
          appBar: AppBar(
            actions: <Widget>[
              FlatButton(
                  child: Text('addFile'),
                  onPressed: () {
                    Provider.of<MyState>(context).changeText("addFile");
                  }),
              FlatButton(
                  child: Text('deleteFile'),
                  onPressed: () {
                    Provider.of<MyState>(context).changeText("deleteFile");
                  })
            ],
          ),
          body: Child(),
        ));
  }
}

class Child extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    MyState myState = Provider.of<MyState>(context);
    return Text(myState.getMyText());
  }
}

这是在没有IDE支持甚至编译和运行的情况下进行编码的。但这应该使您朝正确的方向前进。